1. Field of the Invention
The invention relates generally to a downhole tool for positioning on a drill or tubing string to impart rotational movement to a working implement.
2. Description of the Prior Art
The prior art includes various types of electrical or hydraulic motors that may be included in a sub element along a drill string to impart rotational drive to an associated well tool. In addition, the drill string itself may be capable of rotation to provide the requisite function during drilling operations; however, a tubing string is not capable of controlled rotation and, therefore, a separate rotational source must be supplied and these usually take the form of electrical or hydraulic motors located in a suitable drive sub to provide drive to a working tool therebelow. In many operations, a prolonged or continuous rotation is not required whereupon a controlled rotation device such as the present invention may be acceptable. Thus, the device capable of a predetermined number of finite rotations may be suitable in various downhole operations to operate a recovery tool or the like under control of a surface position.